If you don't want to go w/ Cal-Tracs and their monoleaf springs, I'd look into the Launcher springs...made by Tri-City Competition, Greg Luneak in California.
Stay away from the MP SS springs unless you can find an old set of the good ones. The new ones are junk.
The launchers will ride rough and bouncy on the street. The Cal-Tracs are better IMO and you can back off the preload on the bars when you street drive it to make it more comfortable.
And guys are as fast/faster on Cal-tracs that ladder bars and even in the 1-teens 60 ft. iirc plus like said above, you can back em off for street driving............